Fractures of the tibia or fibula, strains or torn ligaments in the ankle or in the foot are usually accompanied by considerable pain and rapid swelling in the area affected. In some cases it is necessary to "set" a fracture, while in other cases, notably a fracture of the fibula, the physician usually does not perform any setting operation. In both situations the important factor is to immobilize the entire lower leg, ankle and foot, after which the healing of the situation occurs by natural processes.
The general problem encountered is well described in prior art patents such as LOAKSO U.S. Pat. No. 3,215,137 of Nov. 2, 1965, QUICK U.S. Pat. No. 3,314,419 of Apr. 18, 1967 and ROSOFF U.S. Pat. No. 3,880,155 of Apr. 29, 1975.
The common practice in the case of what is believed to be a fracture of the lower leg is first to take all weight off the leg, to temporarily immobilize it by the use of splints, bandages or a preformed shell, and to transport the patient to a place of examination and treatment such as a first aid station, an emergency vehicle, or a hospital. The leg is examined usually by a physician, by x-rays, and a determination is made as to whether it needs to be "set", i.e., to have the broken bones aligned. The next procedure is for a physician to apply a plaster of paris cast which is done by wrapping a fabric bandage impregnated with the plaster which has been wet with water, around the entire area in which the fracture occurred. It is likewise common practice to first apply a loose woven sock over which the plaster cast is developed and then allowed to harden. Care must be taken during this operation to insure that the foot is at the normal approximate right-angle position to the leg and that it is also aligned in a proper crosswise direction. As mentioned, it is important that the foot be in a neutral position so that the Achilles tendon is maintained at a proper position. However, when a patient is told to maintain his foot at the neutral right angle position, during the application of the cast, it is common for the patient to allow his foot to droop and in effect the neutral position is not maintained. It is also important that the ventrum of the foot be supported with neither eversion or inversion. However, some inversion tends to be natural and again, the very position of forming a plaster cast often results in inadvertently inducing eversion or inversion. Additionally, in the case of fractures of the small bones of the foot, the surgeon must maintain a proper longitudinal and transverse arch relation, and he does so by physically molding the bottom of the cast into place.
If the plaster cast has not been properly applied or if the cast becomes uncomfortable due to edema or becomes loose due to the fact that it was applied when there was considerable swelling, it may become necessary to saw off the cast and reapply another.
Frequently, the accident which resulted in the need for the walking cast in the first instance has also resulted in a wound which requires stitching and/or dressing. In such instances, it is necessary, after the cast has been applied, to cut a window in the cast for access to the wound area.
Besides all of the other difficulties of plaster casts, they must be maintained totally free of moisture. However, the wearer must get around and many times it is not possible for the wearer to avoid getting the cast wet, particularly along the bottom of the cast which can come into contact with snow or standing pools of water. Further, the bottom of a walking cast is subject to physical abrasion at the toe and heel portions during walking.
While a stockinet or webbing is initially applied, after a period of use it often tends to wrinkle and may actually rot away, leaving the skin of the wearer in direct contact with the plaster resulting in blisters or pressure sores.
Other problems which are not immediately apparent except to physicians include the necessity to estimate the weight and activity of the wearer, in order to determine how thick the plaster should be applied to provide sufficient strength. If the cast is too light for the person involved and his activities, it will crack requiring the same to be removed and replaced.
Plaster casts are made and applied usually in a specific room for this purpose. Not only is this a time consuming process for both parties, it is inherently a messy process. Either the doctor applying the cast must either fully protect his clothing with disposable garments, or he must change his clothes afterwards.
Additionally, many victims of an accident requiring a walking cast are old or infirm or are non-athletic and have great difficulty walking on the cast due not only to their weight but to the position and height of the non-removable walking apparatus applied to the bottom of the cast. The difficulty often poses a real threat of injury to the wearer in getting around. While the cast is drying, a large number of persons will find that they simply cannot or will not manage with the crutches and will lose two or three days of actual time or loss of work and some will utilize crutches or a cane for the entire time cast is worn.
Still further a cast which is worn for an extended period may result in objectionable odor, severe itching and a general sense of discomfort. A prolonged period of immobilization results in loss of muscle power and this can only be restored by use over a period of days or weeks.
Following application of the cast after a short interval, for example, 15 to 30 minutes, the cast has a preliminary set sufficient to allow the patient to walk on crutches, but it is usually 24 to 48 hours before the plaster has set sufficiently to allow weight bearing. The cast applied is relatively heavy, for example of the order of 10 pounds in the case of a large adult male. The cast may be what is known as a "walking cast" in which there may be a circular stem centrally on the bottom side of the cast of a diameter for instance of 2 inches, or it may be a U-shaped walking iron approximately one-half inch in width. In either case there is no broad support and stability is minimal particularly on ice, water and snow. If the stem or walking iron is too far forward or backward so that it alters the center of gravity of walking, this could clearly cause problems.
The intent is for the patient to use the crutches for supporting the major part of his weight while the plaster dries and from that point on to gradually shift the weight from the crutches to the walking cast.